The causes of Alzheimer's are complex and still being unravelled. Its incidence is increasing as people live longer, including in countries with healthier diets than the UK. This tells us there are many things to take into account. While diet can affect the risk of developing this disease, other factors including genes, environment and life events are important too.

Alzheimer's Research UK has a diverse £18.5m research programme, including studies into the links between diet, diabetes and Alzheimer's. We still need significant and sustained investment in research, by charities and government.Simon RidleyAlzheimer's Research UK

• George Monbiot rightly demonstrates concern around obesity levels and the impact this could have on the development of chronic diseases such as Alzheimer's. UK food and drink manufacturers are keen to do their part to improve public health and have shown leadership in this debate, demonstrating that voluntary action really can deliver in many key areas such as nutrition labelling, reformulation and innovation.

Complex problems like obesity require a wide range of interventions and the involvement of many interested parties to drive real changes in behaviour. Shared responsibility is the founding principle of the Department of Health's Responsibility Deal. Through the deal, UK food and drink manufacturers are working in partnership with government, NGOs and others to tackle the complex causes of obesity and poor public health. The Responsibility Deal is an important part of the UK food manufacturing industry's commitment to achieving responsible and sustainable economic growth. Barbara GallaniFood and Drink Federation

• When it comes to alternatives to nudging, Lord Krebs is stuck in the old policy rut, where a government's only options are education, regulation and taxation (Coalition nudge tactics 'not society's panacea', 6 September). Other options exist to tackle the obesity epidemic. First, it is possible to reformulate popular foods, gradually reducing their fat, sugar and calorie content. Second, it is possible to make them cheaper than standard alternatives. After the pasty tax fiasco, the lesson is clear: instead of taxing "bad" foods, make "good" foods cost less.

At present, healthier options often cost more because companies charge a "health premium". They reason that the nutritionally aware, usually affluent, will pay more for foods they think will do them good. This is nutritional extortion. Cutting excessive margins would give consumers an economic incentive to choose healthier options. "Corporate social responsibility" for food companies should now be defined as: make the healthy choice the cheaper choice.

For 30 years, British governments of both colours have been exhorting people to make "informed healthy choices". That educational strategy has failed. We keep getting fatter and fatter. It is time to get out of the rut, to do something different. Krebs is right that nudging will never suffice. Nutrition policy for the future requires a combination of product reformulation and incentive pricing.Jack WinklerLondon

• The growing evidence that academies have patchy nutrition standards is shameful (Academies bring banned junk food back to school meals, 10 September). Cynics might say this provides a natural experiment: let's see which schools perform better – junk versus better food. But this is an experiment the British have been running for a century or more. I am a fan of Jamie Oliver's actions since 2005, but the struggle to improve nutrition standards began in 1980 when the Thatcher government abolished them. Far from fighting over health standards, school meals now ought to be aspiring to full dietary sustainability, linking health, environment, social values and economy. That's the 21st-century challenge.Tim LangProfessor of food policy, City University